This invention relates to an apparatus for separating a stack of documents, such as, for instance, a stack of magazines, into individual documents.
In practice, there is a regular need to unstack stacks of documents, such as, for instance, magazines, so that individual documents are obtained. In the following, a document is understood to mean not only a magazine, but also a book, a video cassette, a compact disk, a postal item or a like information-carrying object. In the case of magazines, for instance, it is customary for the retailer to return to the publisher the magazines that have not been sold by the end of the day, week or month for which they are intended. Needless to say, the retailer does not first sort the magazines, but returns them to the publisher in often random stacks. Depending on the number of returned magazines and the price of the various magazines which have been returned, the publisher settles with the retailer. It is therefore essential that it be determined how many magazines of each type have been returned by the retailer. Determining these numbers manually is an impracticable task. Specifically, unstacking a random stack of magazines of different types presents a major problem. The object of the invention is to provide an apparatus and a method for separating a stack of documents into individual documents.
EP-A-0 478 981 discloses a method and an apparatus for separating a stack of documents. The known apparatus comprises a horizontal endless conveyor and an inclined roller conveyor. The rollers of the inclined roller conveyor are individually drivable, so that the mutual distance between the documents to be separated is controllable. Apart from the fact that the known apparatus is rather costly, the chances that a proper separation occurs are not particularly high. A first drawback of the known apparatus is that it works exclusively on the basis of the frictional force between the lowermost document resting on the rollers of the roller conveyor and the rollers. This frictional force is dependent on the mass of the document. Specifically with light documents, the frictional force will be small and the chances of the document not being carried along by the inclined roller conveyor are considerable. A second disadvantage of the known apparatus is that the angle of inclination of the roller conveyor in the known apparatus may not be too steep because otherwise the frictional force between the rollers and the underlying document will be too small. For the known apparatus, an angle of inclination of 20.degree. is proposed. Such an inclination is rather gentle. The tendency of the overlying documents to slide down is therefore not all too strong. The known apparatus will therefore be unable to accomplish a proper separation in all types of documents. Moreover, the known apparatus can work only at a relatively low processing rate.